1. Field of the Invention:
The present invention concerns an interface module between a field bus and electrical equipment controlling and protecting an electric motor, this module including an integrated circuit having data pins connected via interface circuits to contacts (or binary sensors) and to coils (or actuators) of the electrical equipment.
2. Discussion of the Background:
Various combinations of electrical devices known as motor starters are used to control and protect electric motors, including direct on-line starters, reversing starters, star-delta starters and progressive starters.
The control function of such equipment uses one or more contractors. The functions which protect the motor against overload, phase imbalance and short-term overcurrents are implemented by various devices or modules: thermal overload relay, motor circuit-breaker, thermal overload protection module incorporated into a motor circuit-breaker or thermal-magnetic module added to a contactor/circuit-breaker.
Consideration has already been given to controlling circuit-breakers via a communication bus which is part of an industrial local area network. This form of control is not suitable for electric motors.
The ASI (Actuator Sensor Interface) field bus for sensors and actuators is used to connect binary actuators and sensors via interface modules, the bus being also connected to a control brain (PC, programmable automatic controller, etc). The bus is a two-wire bus and carries the power supply to the sensors and the information signals travelling between the interface modules. Each module comprises electronic circuitry including an integrated circuit and can drive four standard actuators or read the outputs of four standard sensors, or provide a combination of two inputs with two outputs. The electric circuitry of the module processes data on four bits for each sensor (input) or each actuator (output).
The above interface module cannot be used for motor control since the number of items of data to be processed exceeds four in this case.